They Brew it, I sell it, You Drink it... and so do I..

Tuesday, 7 June 2011


We've all heard of the phrase: this beer is 'skunked'. Until now I've never had a skunked beer in my life, I'm a good ghost who keeps his beer out of range of the evil sun. You may or may not know that the hops used in the 'making beer' process have a certain dislike of UV rays. These evil UV rays which so many people love for making them tanned, will also make your beer taste bad, so they say. The UV rays take a certain dislike to some hop compounds and break them down, causing the beer to have a certain off flavour.

It has been said that clear and green glass offers no protection against the sun and only brown glass can ward off these devious rays. Or so I've been told.

I wanted to indulge in a little experiment today.

Above are 6 bottled beers. 3 of these beers have spent over 4 hours in direct sunlight, and in that time they became rather warm. (very warm indeed actually!) These 3 were then put back with their counterparts and mixed up so I wouldn't be able to make any pre-conceived tasting notes in my brain about what may occur.

I started off with the Brooklyn Lager.

A beer being packaged in brown glass, I was under the assumption that 4 hours under the guns wouldn't affect it. But I was also interested to see if a very high temperature change would affect the beer at all. It seemed I needn't worry at all though. Both beers looked, smelled and tasted exactly the same. A win for the brown beer bottle then, and for Brooklyn beer too. Not only did it withstand 4 hours in the sun, but it also withstood being roasted to the gills! Well played indeed Brooklyn.

Next up was the Tsingtao.

On the pour nothing looked out of the ordinary. In fact when I lifted the glasses to the nose, no un-trained (or trained for that matter) aromatic professor would be able to tell the difference between these beers.

What of the taste though. Well to be perfectly honest, I couldn't find a single difference. It seems that Tsingtao has the same luck in the draw as Brooklyn Lager. Both beers were tamely delicious.  Could it be that the rice used in the production of this beer has some UV preservative qualities? Probably not, but it passed my test.

On to the last beer and offending glass transparency: Tooheys Extra Dry.

Once again there was not much difference to the aromas of the two. In fact there was no difference at all.

If there was a beer which you thought would not pass the test, you'd think it this one. But NO!

I didn't understand. It tasted exactly the same in both glasses! What was going on, I wondered to myself? Did I not leave it in the sun long enough?? Did it even have hops in it?? The bottle didn't state that it did.

Maybe I was just trying to make excuses. It's not a bad beer. It won the Gold Medal in the category for best dry lager in the 1998 World Beer Cup, so it must have hops in it at least.

What's going on!?!?

I'm no bio-chemist, I'm not even any form of chemist. But I left 3 of these beers in direct sunlight for over 4 hours!!! And they all got to a temperature of that well above of your average take away pizza!!! Please tell me what I've done wrong because:

I've tried this experiment with three bottle shades, and yet to have tried a 'Skunked Beer' in my life!!!


  1. First thing that comes to mind is that if you have double glazing the UV wouldn't get though in any case

  2. There are at least three explanations:

    1. You are not sensitive to skunk smells.

    2. The clear bottled beers are made with hop extract that is treated to avoid the effect of skunking.

    3. The beers that are prone to skunking, are already skunked. You may already associate the skunk aroma with beer. Apparently they become skunked quite quickly and can even be effected by fluorescent lights.

  3. Steve, I'm not convinced double glassing stops UV. If so then we could start using the same glass for beer bottles.

  4. Perhaps skunking is a myth? Or possibly you've just proved that the ozone is fixed? Either way I think Dave Cameron needs to axe Trident and order Ossie to initiate Project Skunk

  5. Steve - No double glazing was involved.

    Dave, your 1 + 2 explanations make perfect sense, but I'd be dubious about the third. (but if I'm impervious to skunk aromas I will call myself a modern superhero from now on!)

  6. just reading wikipedia which pointed to this book. interestingly it said using hop extracts can overcome the skunking by avoiding isohumulones getting into the beer in the first place.

    Interesting experiment though!

  7. Ah see Dave already commented similarly with point 2.

    Double glazing wouldn't be practical for bottles Dave! I'm not sure whether its a coating on the glass or the fact that the light is refracted twice. I've read an article in a chemistry mag about it though. That's why people don't tend to get suntanned in their living rooms but can get tanned through a closed car window.

  8. I know from the Beer Bloggers Conference that I'm not as sensitive as some people. Apparently it is possible to be completely immune.

    Apparently, just to make the whole situation worse, some people genuinely associate skunking with a quality beer. Really. This was said by one of the brewers sponsoring the Beer BC.

  9. The scientist in me says that your next experiment should be with the brooklyn Lager poured out in a glass in sunlight compared to the beer straight from the darkness bottle - you could always open them both at the same time to ensure the same carbonation/aging/etc?

  10. Baron- but how long should I keep my lager in the glass, in the sun, before I should expect any signs of spoilage??

    I definitely want to do some more experimentation though!!

  11. It was very obvious when I did my light strike experiment. Try using a something like a Brewdog beer, where you know they use lots of whole hops and you should notice it.

  12. From Charles Bamforth's book "Beer Is Proof God Loves Us" (which I know I keep referencing, but it is really interesting):

    "We also exposed bottles of a famous beer in green glass bottles to bright sunlight [...] given to consumers alongside a sample of the beer that had not been "skunked" there was a 2:1 preference for the non-skunky beer, which still leaves a third of people preferring skunky beer."

    Bamforth also talks about Miller pioneering the development of modified hop preparations to prevent skunking in their clear glass bottles.

    Personally I can't yet identify a specific "skunked" flavour and would also like to educate myself in the defect.


  13. As well as using isomerised hop extract, brewers using clear bottles will wash the yeast several times prior to pitching to minimise any hop carryover from the yeast and supernatant.

  14. All this techno talk suggests that if a brewer wanted to produce a beer and use clear glass, they could and it would be safe from getting light-struck?

  15. I'm really not sure what "skunked" beer tastes like. How many people are? Sometimes I come across a rather duff bottle, but I don't know whether that is "skunked".

    Might it be something like "mouse" in cider, which some people can detect while others are completely oblivious?

  16. Dave makes some good points, especially that not everyone is sensitive to skunked flavour. I'm sensitive to it so have rarely found a beer in clear bottles that I liked.

    You should try and leave them for longer to see what happens. I'd also suggest using a different beer. Mark from BeerBirraBier left one Greene King IPA on a windowsill for a few weeks and the other in a dark cupboard. When we tried them side-by-side I was almost sick from the skunked one - it was horrific.

    Try any Shepherd Neame or Badger beer as they are pretty much all affected by lightstrike. It's a moldy, bad breath kind of aroma, a little like rotting veg.

    And you can produce beers which don't get affected as much (Corona is an good example, I'd guess) but it means treating the hell out of it.

  17. Very interesting experiment, from the sounds of it it just needed more time to spoil.

    Does that mean beers left under the lights on a pub's back bar display do not skunk?

  18. Interesting experiment, now repeat it, but leave the bottles in a windows sill for a week and see what happens... I think Mark's idea of using Greene King, Sheps, or Badger is a good idea too.

  19. Mark are you suggesting that Shepherd Neame or Badger beers are likely to already be light struck, as they come in clear bottles? Or that they are good candidates for use in another experiment?

  20. The scientific approach of course is to take two hoppy beers, pop the caps, decant one into a clear clean bottle, recap, leave on windowsill for a day and compare.

  21. I did a similar experiment a couple of years ago with Heineken. There was a huge difference! Then again, I left it out in the blazing sun for days.